CODEWITHSUNDEEP
javaandroiddependency-injectiondagger
bsr
bsr

Reputation: 58662

Dagger: Field Injection in POJO

I never tried Guide or other DI library, but trying to use Dagger from square for Android application. It works great for Frgements, but not for POJO. The user guide assumes some knowledge on DI as it doesn't explain in greater detail. What should I do to inject restAdapater into my POJO. If I do field injection, with the same code, it works in Fragment.

public class MyApplication extends Application {
    private ObjectGraph objectGraph;

    @Override
    public void onCreate() {
        super.onCreate();
        objectGraph = ObjectGraph.create(new DIModule(this));

    }

    public ObjectGraph objectGraph() {
        return objectGraph;
    }

    public void inject(Object object) {
        objectGraph.inject(object);
    }

    ...
    @Module(entryPoints = { 
    MainActivity.class,  
    .....,
    Auth.class, 
    RestAdapter.class
    })
    static class DIModule {@Provides
        @Singleton
        public RestAdapter provideRestAdapter() {
            return new RestAdapter.Builder().setServer(
                    new Server(Const.BASE_URL)).build();
        }
    }
}

//POJO

public class Auth {

    @Inject
    RestAdapter restAdapater;


    String Username;
    String Password;

    public String authenticate() {
     ...

     Api api = restAdapater.create(..)  // **restAdapater is null**

     }
}

All the fragments are derived from the below, and DI works fine in them. In a recent talk by Eric burke, he explains this is necessary because Android constructs the object.

public class BaseFragment extends Fragment {
    @Override
    public void onCreate(Bundle state) {
        super.onCreate(state);

        ((MyApplication) getActivity()
                .getApplication())
                .inject(this);
    }

}

Upvotes: 3

Views: 2805

Answers (1)

paulboony
paulboony

Reputation: 188

If you create an Auth instance yourself, then Dagger wouldn't be aware of this instance and will not be able to inject the dependencies for you.

Since you have already declared Auth.class in the Module entryPoints, you just need to ask ObjectGraph for Auth instance:

Auth auth = objectGraph.get(Auth.class);

Dagger then would know what is required to provide an instance of Auth, i.e. inject it with your RestAdapter.

Upvotes: 8

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